synonymist vs lexicographer

synonymist and lexicographer both are nouns.

Word	Noun	Adjective	Verb	Adverb
synonymist	Yes	No	No	No
lexicographer	Yes	No	No	No

As nouns, lexicographer is a hypernym of synonymist; that is, lexicographer is a word with a broader meaning than synonymist:

synonymist: a student of synonyms
lexicographer: a compiler or writer of a dictionary; a student of the lexical component of language

Other hypernyms of synonymist include lexicologist.

synonymist (noun)	lexicographer (noun)
a student of synonyms	a compiler or writer of a dictionary; a student of the lexical component of language